1. Field of the Invention
The present invention relates to a sustained releaser and a pest control method each enabling simultaneous release of sex pheromone substances.
2. Description of the Related Art
Currently, as one of the most effective methods for utilizing a sex pheromone of an insect pest, the mating disruption method which confuses the mating behavior of the insect pest by retaining a chemically synthesized sex pheromone substance at a predetermined concentration or greater in a farm field has been developed to a practical stage. What is important in this method is development of a sustained release formulation releaser (dispenser) capable of releasing a synthesized sex pheromone substance for a long period of time at a fixed rate or greater and setting of a period required for mating disruption of an insect pest to be controlled.
In most cases, it may be relatively easy to control the release of a sex pheromone substance of a single insect pest at a fixed rate for a predetermined period, because it contains only one substance, or a plurality of substances which are similar in chemical structure. Some insect pests however have, as their sex pheromone substances, a plurality of compounds utterly different in chemical structure. It is difficult to enclose them in one releaser (dispenser) and control the release of them. In general, a certain crop rarely has a single insect pest fauna so that it is necessary in most cases to control a plurality of insect pests simultaneously, especially in an area having complex insect pest faunas such as Japan.
Difficulties in designing of a sustained releaser capable of simultaneously -releasing compounds different in chemical structure are described below:
(1) The release of compounds cannot be controlled because of a large difference in boiling point (vapor pressure) due to a difference in functional group.
(2) The release of compounds cannot be controlled because even if they are compounds having the same functional group, they differ greatly in a boiling point (vapor pressure) owing to a difference in the number of carbon atoms.
(3) A formulation supported on a porous carrier having no barrier properties will inevitably release a compound having a higher vapor pressure faster even if an evaporation area is made equal. An additional difficulty in designing a releaser for simultaneous control of insect pests is that these insect pests have their own infestation period.
Among pest insects, there are many insect pests having an aldehyde compound as a sex pheromone substance, for example, Chilo suppressalis, Helicoverpa assulta, Helicoverpa aarmigera, diamondback moth, Caloptilia theivora Walsingham, Dichocrocids punctiferalis Guenee, navel orange worm, spiny bollworm and Parapediasia teterrella. 